Screening of Brazilian Bacillus sphaericus strains for high toxicity against Culex quinquefasciatus and Aedes aegypti

Abstract:  In this work, 246 Bacillus sphaericus strains were evaluated against Aedes aegypti and Culex quinquefasciatus larvae to select the most effective ones to be used as the basis of a national product. All strains were isolated from different regions of Brazil and they are stored in a Bacillus spp. collection at Embrapa Genetic Resources and Biotechnology. The selected strains were characterized by biochemical and molecular methods. Based on selective bioassays, 87 strains were identified as toxic to one or both target species. All of these strains contain genes that encode the 42, 51 kDa proteins that constitute the binary toxin and the 100 kDa Mtx1 toxin. All toxic strains presented a very high LC₅₀ against A. aegypti , so, a product based on any of these B. sphaericus strains would not be recommended for use in programmes to control A. aegypti . S201 had highest activity against C. quinquefasciatus , presenting the lowest LC₅₀ and LC₉₀ in bioassays.     

Interhabitat and instream movements of large Atlantic salmon parr in a Newfoundland watershed in winter

Radio‐telemetry was used to investigate movement of large, mainly mature male (80%) Atlantic salmon Salmo salar parr in Stoney River, Newfoundland during early winter (November; water temperature 6·0 ± 0·1° C) and mid‐winter (January to February; 0·8 ± 0·0° C). Site fidelity of parr in early winter was low. Parr moved between fluvial and lacustrine habitats and were active throughout the diel cycle. Parr caught in fluvial habitats in mid‐winter were smaller and younger than parr caught in early winter. Site fidelity of parr in mid‐winter was greater than in early winter. Parr in mid‐winter moved between fluvial and adjacent small lacustrine habitats, but avoided a larger pond inhabited by large piscivorous fishes. Instream movement rates in mid‐winter were lower than in early winter and occurred primarily during hours of darkness (dawn, dusk and night). Fluvial habitats were relatively stable and ice‐free throughout the study periods. These results suggested that large Atlantic salmon parr utilize a variety of habitats and remain active throughout the winter, even under stable environmental conditions.     

Expression of the vesicular stomatitis virus nucleocapsid protein controlled by the lambda PR and PL promoters in Escherichia coli

Expression vectors were constructed in which a cDNA specifying the vesicular stomatitis virus nucleocapsid (VSV N) protein was inserted near the translational initiation region downstream from the thermoinducible P_R or P_L promoter of bacteriophage λ. Expression of the VSV N-protein was determined by a radioimmunoassay with monoclonal antibody prepared against the VSV N-protein. The expression of the VSV N-protein in Escherichia coli was low with either system. However, the deletion of a part of leader sequence from the translational initiation signal to the VSV N-gene resulted in at least 30-fold increase in production of the VSV N-protein. The VSV N-protein in E. coli was also analyzed by radioimmune blot after separation of proteins by gel electrophoresis. Degraded proteins reacted with the antibody were also observed in the cell extracts.     

DNA重组酶Cre介导载体间基因的重组转移

DNA重组酶Cre可以识别LoxP位点,使含有LoxP位点的DNA分子发生重组:2个同向LoxP之间的DNA片段被删除,2个环状DNA分子被整合为一个大分子.基于Cre酶的这些作用特性,构建了一套载体间基因的重组转移体系,在Cre酶的作用下,gfp基因被从基因供体pTLG上切除下来,然后转移到基因受体pET-LoxP上,从而快速、简便地完成了gfp基因高效表达载体pET-gfp的构建.gfp基因在大肠杆菌BL21(DE3)中被诱导表达,使菌落产生了可视的绿色荧光.通过对荧光菌落的计数分析,比较了环状基因供体pTLG和线性基因供体pTLG对有效重组率的影响.使繁琐的传统载体构建变为简单的酶促反应,极大地简化了载体构建步骤,为Cre酶在基因克隆和亚克隆中的应用提供了很好的研究基础.     

Measurement of Horizontal and Vertical Movement of Ralstonia solanacearum in Soil

Two model systems were constructed to measure horizontal and vertical movement of bacteria in soil. These systems were applied to measuring movement of Ralstonia solanacearum (race 1, biovar 3), a causal agent of bacterial wilt of tomato, in andosol and sand at 28°C. The first system was used to measure horizontal movement of the bacteria in soil packed in a narrow horizontal frame. Suspension of the pathogen was applied to soil at one end of the frame, and bacterial number per gram of soil was measured over distance from the inoculation point after 4 days. Horizontal movement of R. solanacearum in supersaturated soil, but without flow, was possibly due to diffusion and the front advanced at 2.2 cm/day in andosol, and at 8.1 cm/day in sand. Using the same experimental system, but applying water inflow to one end of the frame only, the bacterium was detected at the front of water in andosol and sand. The front of the distribution advanced at 20.4 cm/h in andosol and 66.3 cm/h in sand. In the second experimental system, a cylinder of soil packed in a short tube was soaked with water, and soil at the top of the tube was inoculated with bacterial suspension. Immediately, soil cylinders were turned upward, and the bacterial number per gram of soil was measured along vertical distance from the inoculation point after 7 days. Using the system with andosol, the capillary water front rose to 32.5 cm over 7 days after inoculation, and R. solanacearum reached to 18.8 cm height. In sand, capillary water rose to 20.0 cm and the bacteria reached to 16.3 cm height.     

Tumor-specific gene expression patterns with gene expression profiles

Gene expression profiles of 14 common tumors and their counterpart normal tissues were analyzed with machine learning methods to address the problem of selection of tumor-specific genes and analysis of their differential expressions in tumor tissues. First, a variation of the Relief algorithm, “RFE_Relief algorithm” was proposed to learn the relations between genes and tissue types. Then, a support vector machine was employed to find the gene subset with the best classification performance for distinguishing cancerous tissues and their counterparts. After tissue-specific genes were removed, cross validation experiments were employed to demonstrate the common deregulated expressions of the selected gene in tumor tissues. The results indicate the existence of a specific expression fingerprint of these genes that is shared in different tumor tissues, and the hallmarks of the expression patterns of these genes in cancerous tissues are summarized at the end of this paper.     

Movement patterns of Cephalopholis cruentata in a marine reserve in St Lucia, W.I., obtained from ultrasonic telemetry

Home range size and shape, and within home range movement patterns were determined from 10 adult graysby Cephalopholis cruentata implanted with acoustic transmitters on two reefs within the Soufriere Marine Management Area, St Lucia. The mean home range area was 2120 m²(range 1200 to 4000 m²) and non‐circular in shape. All fish demonstrated a clear preference for a specific area in their home range where, on average, 72·9% of an individuals position were located. Time spent in this favoured area was correlated with reef complexity. Fish with greater activity and displacement possessed a larger home range. Activity and displacement were higher by night than by day, and consistent with this, fish spent less time in the preferred area of their home range by night than by day. Tagged individuals demonstrated a strong tendency to avoid sand habitat present at reserve boundaries.     

Landscape scale, heterogeneity, and the viability of Serengeti grazers

Species persistence can be threatened by substantial temporal variation in food resources over time. On the other hand, spatial heterogeneity in resources at the landscape scale might allow mobile consumers to compensate for temporal variability in resource availability at the local scale. We evaluated this hypothesis, using an extensive data set on foraging, grass growth, and movement by Thomson's gazelles living on the Serengeti Plains. Here we show that modelled populations of Thomson's gazelles can only persist under Serengeti conditions in the face of observed levels of rainfall stochasticity by making adaptive movements to take advantage of ephemeral spatial distributions of food resources. More importantly, our models suggest that Thomson's gazelles in Serengeti require unrestricted access to relatively large areas of grassland (> 1600 km²) to guarantee long‐term persistence, particularly when there is positive spatial autocorrelation in resource abundance, as is the case in Serengeti. If this proves to be true for other species and/or other systems, then understanding of complex behavioural responses to spatially and temporally heterogeneous food supplies may be essential to successful conservation of grazing herbivores.